This is a continuing study in comparative oncology, designed to identify and characterize neoplasms in lower animals including all the cold-blooded vertebrates and all the invertebrates. By studying neoplasms in animals phylogenetically more remotely removed from man, it is hoped to gain a more complete understanding of the basic biology of neoplasia at all phylogenetic levels. It is expected that such studies will reveal properties of neoplasia not previously suspected to exist because of the excessivley narrow scope of studies limited to the higher animals and man. Important differences in the immunologic, biochemical, and regenerative characteristics of the lower animals should serve to emphasize the relevance of these characteristics to the development of and the susceptibility to neoplasia. In addition, by study of neoplasms in lower animals under feral conditions, these neoplasms may be found to serve as indicators of environmental tumorigenic agents. Neoplasms are collected, either in the field or through submittal from outside sources, and are studied morphologically and biologically. Light and electron microscopy are used with fixed material. Tissue culture, transplantation, and induction methods are applied to study phenomena such as regenerating dedifferentiation, autotomy, graft rejection, tumor progression, and others.